Many-Electron Theory of Atoms and Molecules. V. First-Row Atoms and Their Ions

Abstract

The correlation energies of the 1s^22s^2 inner cores of the first‐row atoms B, C, ···, Ne are found to be very different from those of the corresponding four‐electron Be‐like ions, B^+ to Ne^(6+), due to the exclusion effects of the outer 2p electrons. Whereas the 2s^2correlation, ε(2s^2), in the 1s^22s^2 ions increases from —1.13 eV in Be to —3.2 eV in Ne^(6+), the 2s^2 correlation in the neutral atoms decreases from —1.13 eV in Be to —0.27 eV in Ne. The many‐electron theory was used for the nonempirical 2s^2 calculations and included the use of the r(12) coordinate. With these theoretical ε(2s^2) values the correlation of a 2p electron with the 1s^22s^2 inner core is found to be large, ∼—1 eV. Also the 2p^2correlation comes out about —1 eV. The results show that core energies will, in general, depend strongly on the state and number of the outer‐shell electrons and that intershell correlation interactions may be appreciable. Implications for π‐electron systems and the ligand‐field theory of inorganic complexes are discussed.